This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The investigation of venoms is focused on the knowledge of the components directly related to the toxic effects for humans, but many components directly related to the toxic effects for humans, but many components have a broad spectrum of biological activities. This, in addition to the medical reasons, the study of the composition of the venom has a great interest for the discovery of new biochemical tools for the analysis of the operational mechanisms of the nervous system and cellular membranes. It has been reported that scorpion venom contains a variety of biologically active components: enzymes, peptides, nucleotides, lipids, biogenic amines and other unknown substances. Scorpion venoms are rich sources of peptides with a variety of pharmacological functions. Known pharmacological activities include antimicrobial, anti-epilepsy, insecticide, phospholipase and toxins. The scorpion Vaejovis mexicanus smithi is native from the state of Morelos, Mexico. This species has not been studied in depth previously. Preliminary studies have shown a complex mixture of components present in its venom, which makes it an interesting target of study for the search of new bioactive components. Crude venom was fractionated by RP-HPLC, and around 85 fractions were collected. Each fraction was subjected to MALDI-TOF mass spectrometry. The approximate size of different cannel-blocking peptides has been previously reported. Fractions containing components of such molecular masses were selected for further studies. Due to the complexity of the mixture and the size of the peptides of interest, Edman sequencing as well as LC/MS, CID and ECD could be utilized in order to decipher the amino acid sequence of the toxin components. A combination ECD analysis and selective N-terminal labeling can aid the de novo sequencing of large peptides.